H.L. Gerrits

Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

Study design: A longitudinal training study. Objectives: To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training. Settings: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands. Methods: Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE. Results: Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaffected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses. Conclusion: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which reflect an early response of long-term disused muscles. Spinal Cord (2000) 38, 214–223

Variability in fibre properties in paralysed human quadriceps muscles and effects of training

A spinal cord injury usually leads to an increase in contractile speed and fatigability of the paralysed quadriceps muscles, which is probably due to an increased expression of fast myosin heavy chain (MHC) isoforms and reduced oxidative capacity. Sometimes, however, fatigue resistance is maintained in these muscles and also contractile speed is slower than expected. To obtain a better understanding of the diversity of these quadriceps muscles and to determine the effects of training on characteristics of paralysed muscles, fibre characteristics and whole muscle function were assessed in six subjects with spinal cord lesions before and after a 12-week period of daily low-frequency electrical stimulation. Relatively high levels of MHC type I were found in three subjects and this corresponded with a high degree of fusion in 10-Hz force responses (r=0.88). Fatigability was related to the activity of succinate dehydrogenase (SDH) (r=0.79). Furthermore, some differentiation between fibre types in terms of metabolic properties were present, with type I fibres expressing the highest levels of SDH and lowest levels of α-glycerophosphate dehydrogenase. After training, SDH activity increased by 76±26% but fibre diameter and MHC expression remained unchanged. The results indicate that expression of contractile proteins and metabolic properties seem to underlie the relatively normal functional muscle characteristics observed in some paralysed muscles. Furthermore, training-induced changes in fatigue resistance seem to arise, in part, from an improved oxidative capacity.

Effects of training on contractile properties of paralyzed quadriceps muscle

Effects of two different training regimens on the contractile properties of the quadriceps muscle were studied in six individuals with spinal cord injury. Each subject had both limbs trained with the two regimens, consisting of stimulation with low frequencies (LF) at 10 HZ or high frequencies (HF) at 50 HZ; one limb of each subject was stimulated with the LF protocol and the other with the HF regimen. Twelve weeks of daily training increased tetanic tension by ∼20%, which was not significantly different between training regimens. Interestingly, after HF but not LF training, the unusual high forces at the low frequency range of the force–frequency relationship decreased, possibly due to a reduced activation per impulse. After LF but not HF training, force oscillation amplitudes declined (by 33%) as relaxation tended to slow, which may have opposed possible effects of reduced activation as seen after HF training. Finally, fatigue resistance also increased rapidly after LF training (by 43%) but not after HF training. These results indicate that different types of training may selectively change different aspects of function in disused muscles.

Muscle properties and functional recovery until one year after stroke

Purpose: to investigate functional performance in relation to muscle function during first year after stroke. Methods: Maximal voluntary isometric torques of knee extensors (MVTe) and flexors (MVTf) were obtained in 14 patients with subacute stroke (bilaterally) 3.5±2 months after stroke and 3 (n=8), 6 (n=5) and 12 months (n=3) thereafter and in 12 age-matched able-bodied subjects. Maximal triplet response (intrinsic muscle strength), maximal rate of torque development (MRTD) and degree of voluntary activation of knee extensors were estimated. Patients performed 7 tests of functional performance. Results: In the paretic lower limb (PL), all parameters significantly (0.494<|r|<0.909) improved during all follow-ups. In the non-paretic lower limb (NL) most improvement occurred within the first 3 months. For NL and PL, MVTe improved 5 and 16%, respectively MVTf 3 and 20%, triplet 0 and 13%, activation 8 and 9%, MRTD 16 and 61%. Significant correlations (0.460<|r|<0.906) were found between all tests of functional performance and all muscle parameters of PL and all parameters (0.454<|r|<0.873) but triplet and MRTD of NL. Conclusion: All strength parameters correlated significantly with functional performance. Therefore, it is recommended to investigate the role of strength training of both legs during at least the first year of stroke.